Detailed Explanation of Key Technical Points for Safe Overwintering of Rana chensinensis

Rana chensinensis is an important economic frog species in China, with extremely high culinary and medicinal value. Because of its large market demand and increasingly scarce wild population, it has attracted many people to farm it. However, overwintering is a difficult matter in farming, and improper management during overwintering often causes large numbers of Rana chensinensis to die. So how should Rana chensinensis safely overwinter? Let's take a look together.

1. Overwintering adaptation period

There is an adaptation period both before and after overwintering for Rana chensinensis, namely the pre-hibernation adaptation period and the post-hibernation adaptation period. Management during these two periods is extremely important and is the key to whether Rana chensinensis can safely overwinter. Before overwintering, the climate at this time is unstable, and Rana chensinensis is also transitioning from lung breathing to skin breathing, so an adaptation period is needed. As the climate constantly changes, Rana chensinensis adjusts its body functions on its own. When the temperature is low, Rana chensinensis enters the water, and when the temperature rises, it returns to the shore. This repeats several times until it can fully transition to skin breathing, and only then does it normally begin the overwintering period. At this time, if Rana chensinensis is forced into the water to overwinter, it is very likely to be unable to adapt and eventually suffocate to death. Similarly, the post-hibernation adaptation period is the process in which Rana chensinensis ends dormancy and begins to come ashore. In spring, the temperature difference between day and night is large. When the temperature is low, it will seek hidden cover to adapt to the environment. If there is no suitable place for it in the site, it will also die.

2. Overwintering in overwintering ponds ⟧7⟧The main overwintering methods currently used in Rana chensinensis farming are facility overwintering ponds and cellars. Facility overwintering ponds refer to building overwintering ponds in a greenhouse or conservatory environment. Generally, a rectangular water pond is dug, and the depth must ensure a water level of 1 m after freezing, so the specific depth depends on the environment of each region. The sides of the overwintering pond must have slopes to make it convenient for Rana chensinensis to leave the water after overwintering. Devices must be installed at the water inlet and outlet to prevent leakage. Some stones can be placed at the bottom of the overwintering pond to simulate the wild environment. After the pond is built, disinfection measures must be taken well to avoid infection by pathogens during overwintering. Also pay attention to the harm from snakes and rats. Overwintering can begin when the water temperature is higher than the air temperature. Generally, about 300 Rana chensinensis are placed per sq m. During overwintering, equipment can be used to keep the pond water slightly flowing. The water needs to be changed once every 10 days. When changing the water, do not replace all the water at once. Generally, replace one-fifth to one-third each time, so that the water temperature difference does not exceed 2°C. After changing the water, aerate promptly. Keep the dissolved oxygen in the water body at 7-9 mg per liter. When oxygen is insufficient, change the water promptly to maintain the dissolved oxygen content. In addition, maintain the water temperature at 2-4°C. The overwintering survival rate is above 95%.

The main overwintering methods used in wood frog farming today are facility overwintering ponds and pit-style overwintering. A facility overwintering pond refers to an overwintering pond built inside a greenhouse or conservatory environment, generally a rectangular water pool dug out, with the depth set so that there is 1 m of water level after freezing, so the specific depth depends on the environment of each region. The sides of the overwintering pond should have sloped ground so the wood frogs can climb out after overwintering, and devices should be properly installed at the inlet and outlet to prevent water leakage. Some stones can be placed at the bottom of the overwintering pond to simulate the wild environment. After the pond is built, disinfection measures should be carried out well to avoid infection by pathogens during overwintering, and attention should also be paid to the harm from snakes and rats. Overwintering can begin once the water temperature is higher than the air temperature, generally stocking about 300 wood frogs per sq m. During overwintering, equipment can be used to keep the pond water slightly flowing, and the water needs to be changed once every 10 days. When changing the water, do not replace it all at once; generally change one fifth to one third each time, so that the temperature difference does not exceed 2 degrees, and aerate promptly after changing the water. Keep the dissolved oxygen in the water at 7-9 mg per liter, and change the water promptly when oxygen is low to maintain the dissolved oxygen content. In addition, maintain the water temperature at 2-4 degrees, and the overwintering survival rate will be above 95%.

3. Overwintering in cellars

Overwintering in cellars is different from overwintering ponds. Overwintering ponds overwinter in a water body, while cellars have no water. When digging a cellar, it should be determined according to the local temperature. Generally, the deeper the cellar, the higher the temperature at the bottom of the cellar, and in the cold regions of Northeast China, a depth of about 2.5 m can be dug. At the bottom of the cellar, at least half a meter of soil layer must be covered, and there must also be a ventilation hole and a cellar door. The ventilation hole should be half a meter above the soil layer on top of the cellar. At the bottom of the cellar, a layer of muddy sand soil can be spread, and then a layer of dead branches and fallen leaves placed on top. This is also to simulate a forest environment so that Rana chensinensis can adapt quickly. 200-300 can be placed per sq m, or correspondingly reduced depending on the situation. During overwintering, control the temperature between 1°C and minus 6°C and the humidity at 80%-90%. The mortality rate is extremely low. Once the temperature is too high, ventilate promptly to cool it down, and if the humidity is too low, spray water mist promptly to increase humidity.

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